Inappropriate suppression of thyrotropin during medical treatment of Graves disease in childhood.

Twenty-nine patients (22 female) aged 2 to 17 years were followed with serial measurements of serum triiodothyronine, thyroxine, and thyrotropin during medical therapy for Graves disease. Fourteen patients had 17 instances of hypothalamic-pituitary-thyroid suppression with inappropriately low thyrotropin levels. Five patients had six episodes of low thyroxine and triiodothyronine levels with normal levels of thyrotropin, and 10 patients had 11 episodes of normal thyroxine and triiodothyronine levels with subnormal levels of thyrotropin. We conclude that thyrotropin values may not be reliable for diagnosing either mild hypothyroidism or persistent hyperthyroidism during the medical treatment of Graves disease.